Christopher Nolan's announcement last year that he would return to direct a third and final Batman film was truly one of those wipe-the-brow moments for comic book fans. A trilogy of movies is just the ticket, and with the excellent Batman Begins and The Dark Knight already in the bag, all Nolan has to do is complete third instalment The Dark Knight Rises without succumbing to Ewok-itis and he's home free. A story on the Hollywood Reporter's Heat Vision blog yesterday offered some tantalising clues as to how he's going to do it.

The site reports that Nolan is screen-testing actors for two female roles in the new film, one a love interest, the other a villain. The quartet being hyped with the most confidence by the blog consists of Keira Knightley, Anne Hathaway, Jessica Biel and Gemma Arterton, with the lesser-known Kate Mara and Charlotte Riley also getting a mention. More intriguingly, it's reported that the villain may well be Talia al Ghul, daughter of Liam Neeson's Ra's al Ghul from Batman Begins.

In the comics, the character is Bruce Wayne's lover and his enemy at different stages, and sometimes both at the same time. Her addition would smartly round off the trilogy, as Batman's actions (or rather inaction) led to the death of Ra's al Ghul in the first film. One can only imagine how Batman 3 might have turned out had Heath Ledger lived – differently I suspect – but in the absence of the Joker, a return to the themes of the trilogy's opening chapter seems a sensible strategy.

If Nolan chooses to make Talia British, one can see why Knightley, Arterton and Hathaway (American but with a talent for accents) may be involved. I can't see the film-maker taking a punt on Mara or Riley for the vital villain's role, though they might work well in a smaller part. Nolan will surely avoid making the love interest role as substantial as that of Rachel Dawes: it would rather diminish Maggie Gyllenhaal's vivacious performance in The Dark Knight, not to mention the stature of the film itself, if Wayne immediately embarked on a new romance in part three. Plus, when the love of your life has just been murdered and you're a masked vigilante on the run from both the cops and the mob, it must be hard to find time to visit singles bars.

Two other actors, Naomi Watts and Eva Green, are apparently out of the running for the time being. Wouldn't Green make a fabulously stylish and exotic Batman villain? Another French actor, Marion Cotillard, has the same spot-on combination of maturity and grace, but Nolan would presumably think twice about casting her so soon after Inception.

Not so Tom Hardy, who is on the castlist and may play another villain. Christian Bale will return as Batman, of course, and Michael Caine will once again be on hand with timely morsels of pithy cockney wisdom as butler Alfred. Nolan plans to shoot in London and Los Angeles, presumably with Chicago also doubling for external shots of Gotham once again (though this report suggests it might be Detroit instead) in May. The film should be completed in time for a 2012 release. It's all shaping up rather nicely, wouldn't you say?

Before I leave you, I couldn't not send you in the direction of this wonderfully candid interview-cum-report in the New York Times which sheds light on the comings and goings at The Green Hornet, which hits cinemas tomorrow. Apparently Nicolas Cage was once going to play the main villain, but walked out due to creative differences – he wanted to do it with a Jamaican accent. Meanwhile, departed director Stephen Chow's ideas included a segue in which Kato controls Britt Reid (aka the Hornet) by remote control via a chip in his head.

For the record, I caught the movie earlier this week and it's a passably entertaining take on the comic book comedy, a sort of superhero bromance really, with Seth Rogen doing his usual gormless clown thing and Christoph Waltz still eminently watchable as the bad guy despite having to get his gums around dialogue unfit to lick the boots of Quentin Tarantino's script for the opening sequence of Inglourious Basterds. There are some standout action sequences featuring Jay Chou's take on Kato, thanks to Michel Gondry's inventive version of bullet time, but the movie does feel a mite clunky and unpolished in spots. While there are myriad references to the 1930s radio serial, this is a distinctly irreverent take on The Green Hornet, but given that most fans of the source material in the house will be dribbling into their popcorn due to advanced age, I think they'll get away with it.